Analog-type constant-current regulator

ABSTRACT

Analog-type constant-current regulator which works as an alternating-current setting controller. It operates with a phaseangle split control and a zero-voltage switch. Across a rectifier, the actual value is impressed as a current. The regulator is suitable in particular for obtaining, independently of the load, a constant, effective alternating current, as a matter of example, for heating protective housings and smalldiameter conduits in which measurements are made of liquid and gaseous substances. The main circuit of the regulator includes a series connection of the load with a transducer forming part of an actual-value rectifier circuit and a control circuit which is preferably in the form of a Triac.

220V AC o United States Patent 1191 1111 3,715,651

Ott v 1 1 Feb. 6, 1973 s4 ANALOG-TYPE CONSTANT-CURRENT 3,353,082 11/1967Mellottetal ..323/22 sc x REGULATOR 3,395,334 7/1968 Stein ..323 22 sc[76] Inventor: Er lch Ott, Rud1ger Strasse 15, Primary Examiner GeraldG01 dberg wlesbaden Germany Attorney-Tab T. Thein [22] Filed: Jan. 4,1971 21 Appl. No.: 103,733 [57] ABSTRACT Analog-type constant-currentregulator which works [30] Foreign Application Priority Data as analternating-current setting controller. It operates with a phase-anglesplit control and a zero-voltage 1970 Germany 20 00 0- switch. Across arectifier, the actual value is impressed as a current. The regulator issuitable in particular for 323/4, 307/252 307/252 obtaining,independently of the load, a constant, effec- 323/22 323/241323/38. tivealternating current, as a matter of example, for [5]] Int. Cl ..G05f1/44, GOS f 5/00 heating protective housings and smalpdiameter com [58]new of Search "323/22 241 341 351 duits in which measurements are madeof liquid and 323/403 41 9; 307/252 252 N1 252 UA gaseous substances.The main circuit of the regulator includes a series connection of theload with a trans- [56] Reterences (med 1 ducer forming part of anactual-value rectifier circuit UNITED STATES PATENTS an? a controlcircuit which is preferably in the form of a -r1ac. 3,538,427 ll/l'970Oltendorf ..323/24 3,577,177 5/l97l Hewlett, Jr ..323/22 SC X 33 Claims,5 Drawing Figures TWO-STEP TEMPERATURE REGULATOR DESlRED-VALUE I ARECTIFIER ll- I /B 1 l M R3? ZERO-VOLTAGE T D SWITCH 1 I l T A w 1232111133pF W tom RA R 1 P -.phuse neutral PAIENTEUFEB 6 I975 SHEET 10F3 FIG. 1 CONTROL RANGE ..BAs|c LOAD IIIII'IIIIIIII I'll- PZwmmDU 0 I0I00 "0 I20 I30 -I80l70 I60 I50 I40 I30 I20 IIO I00 90 80 70 60 50 40 3020 I0 0 ANGLE 0F IGNITION *ANGLE 0F CURRENTFLOW FIG. 2

TWO-STEP TEMPERATURE INVENTOR.

ERICH OTT SWITCH ,1

ZERO-VOLT DESI RED-VALUE RECTIFIER E,H) A

VALUE ER Z- 09, ID

ACTUAL- RECTI FI LOAD p Phase neutral 220V AC AGENT PAIENIEIIFEII 6 Ian3.715551 SHEET 3 0F 3 FIG. 40

. (PRIOR ART) VOLTAGE 7 0R CUR RENT CREST VA LUE 1 PEAK-TO-PEAK U g TVALUE AMPLITUDE AVE AGE R.M.S VALUE VALUE VALUE I 0,6.36) (0.707) I I I45 90 I35 Ieo 225 270 3l5 3'60 I TIME (FIRING TIME) o-E PERIODCONDUCTION TIME= |80-FIR|NG TIME ONE PERIOD FIRING TIME 45 CONDUCTIONTIME |80-45 =I35 ANALOG-TYPE CONSTANT-CURRENT REGULATOR Electricaldevices in which measurements are made of liquid and gaseous substancesare required to have an unchanged effect under varying conditions. Forinstance, in case of tubes or conduits having equal heat losses, theheating of the same requires an identical heating effect for eachdetermined length of the conduit. In the chemical and especially thepetrochemical- These devices are usually provided with active bridgecircuits having a compensated internal resistance. The constant-currentsources derive from the network a constant power fluctuating only withthe networks own voltage. The constant power, after substraction of thenecessary leakage power, is converted to heat either in the deviceitself or in the load. Thus the electrical power leakage results in aheating effect within the device. This means that a great deal of theelectric energy is converted to heat in a place where it is notrequired.

These constant-current sources are not applicable in temperatureregulators whereinthe measurement is carried out subject to thetemperature of the device itself. The reason herefor is that thetemperature measurement is affected by the self-heating of the deviceand thus causes serious errors. Such constant-current sources aredescribed in various publications of the companies Siemens & Halske,lntermetall and RCA.

The publications in question are titled:

Siemens & Halske: Schaltungen mit l-lalbleiterbauelementen lCircuitswith Semiconductor Elements/ lntermetall: Schaltbeispiele /CircuitExamples/ RCA: Silicon Power Circuits Manual.

The company Hartmann & Braun A.G., Germany, discloses such an apparatusin an article entitled Continuous Regulator with a Thyristor SettingAmplifier, in the publication Kunststoffe /Plastics/, 58/1968, vol. 10,pp. 68.1 to 683. This regulator provides a uniform heating of heatingwires while controlling at the same time the energy on the load byalternatingcurrent pulse groups. The current flowing in said regulatoris a quasi-constant alternating current. The current might be designatedas constant if consideration be paid not only, as it is usually done, tothe two sine halfwaves, i.e. to one full cycle, but to a plurality ofpulse groups consisting of a number of half-waves.

As a matter of principle, the alternating-current controller, beingeither a Thyristor or a Triac, is basically ignited after thezero-crossing passage of the network voltage while the second half-waveis necessarily ignited after the first half-wave has been passedthrough. During a single' cycle there always flows a current which isdetermined only by the network voltage and the load. The work, or putotherwise, the heating energy is governed by the change of the relationbetween the switched-on and the switched-off altemating-current cycles.lf integration lasts longer the heat produced is steady. It is thuscorrect to state that the regulator produces uniform heating butaccording to accepted definitions, the alternating current which flowstherein cannot be designated as constant.

It is the object of this invention to provide an analogtypeconstant-current regulator capable of supplying a predetermined, steadyeffective alternating current despite of a varying load. The regulatormust respond to changes in a ratio larger than 1:3. Both half-waves ofthe network voltage should be fully exploited in the regulator so that ahigh percentage of the effective net work voltage can be utilized.

The regulator according to the invention achieves the above objects suchthat it has the input-current flow or forward flow angle coupled as acorrective value for eliminating the effects of disturbance variables.

If the desired-value setting device or circuit is cor- 1 rected inresponse to the current flow angle, then use can be made of anarithmetical average-value rectifier for purposes of an actualvaluesetting circuit. The desired current value is to be corrected to follow,within certain error limits, the equation 1+cos t desu-ed U act 19wherein acf stands for the current flow angle. The factor k takes intoaccount the final value at full 180 modulation. Equations and diagramsfully explaining the considerations underlying this invention are beingpresented somewhat later in the description.

British Pat. No. 821,089 published Sept. 30, 1959, titled VoltageRegulator, issued to Sorensen'Ardag, a Swiss Company (based on a U.S.patent application filed Sept. 24, 1956, discloses analternating-current voltage regulator with a transducer, in which asaturable reactor is coupled between an alternating-current power sourceand the load for controlling an effective alternating-current parameter,namely the voltage. A sensing circuit is disposed across the load, whichis provided with a resistor diode gate connected to a two-way rectifiercircuit. Two potential-free voltages are fed to the gate for making theoutput of the combined diode circuit closely to approach a currentvoltage relationship with a square characteristic. The sensing circuitis connected to a transistorized amplifier which latter is connectedwith its output to and controls the saturable setting reactor of thedevice so that a steady, effective voltage results.

The circuitry described in the foregoing includes a coupling circuitwhich is not suitable for prolonged operation. If under load for acertain period of time, the batteries installed in the device changetheir voltage. They should be substituted by network-fed stabilizedconstant-voltage devices. Besides, from the technical viewpoint, suchdevices are too complex since they include numerous heavy parts, makingthe devices excessively expensive in their production costs.

Thyristors or Triacs if used as final control devices would beconsiderably cheaper; however they cannot be employed in connection withresistor diode gates of such arrangements.

According to important features of the invention, the analog-typeconstant-current regulator comprises an actual-value rectifier uponwhich the actual current is impressed, a circuit for coupling theforward flow angle of the current to the input, as a corrective valuefor eliminating disturbance variables, and a controller, preferably inthe form of a Triac, constituting a final control element for adjustingthe desired alternating current. The corrective value is derived fromthe voltage drop across said Triac. A protective circuit may be addedfor the latter, preferably in the form of at least one RC member, toprevent excess voltage pulses from reaching the same.

According to yet another important feature, a circuit is provided forsetting the desired value, at least within the range of 13 to 150 of theforward flow angle. The setting circuit is preferably in the form of avoltage divider upon which is impressed a positive voltage, corrected bya negative voltage which increases with a decreasing value of theforward fiow angle. A supplemental load may be provided, including, as amatter of example, a Zener diode and at least one resistor.

An additional circuit may also be provided according to the invention,to make the desired value dependent on the voltage divider, andincluding at least one capacitor for suppressing high-frequencyoscillations.

In accordance with further important features of the invention, theregulator may comprise an averagevalue rectifier for measuring the loadcurrent, a differential amplifier upon which are impressed, and whereinare compared, the output of the just mentioned rectifier as well as thecorrected desired value for the setting circuit, a synchronizingcircuit, and an ignition pulse circuit. .T he differential amplifier isconnected, by the intermediary of the synchronizing and the ignitionpulse circuits, to drive the controller, e.g. at the control electrodeof the Triac.

In an exemplary circuit arrangement, the differential amplifier includestwo transistors forming part of a bridge which is balanced when theimpressed voltage values areequal, derived from the actual-valuerectifier and from the setting circuit. The amplifier may include acapacitor which is discharged through the synchronizing circuit duringeach zero-axis crossing of the network voltage. A negative feedback ispreferably incorporated in the differential amplifier.

RC members in an end stage, associated with the amplifier, are providedto obtain an approximately proportional integral regulation.

The synchronizing circuit may be provided, according to the invention,in the form of a zero-voltage switch associated with the controller (theTriac). A phase-correcting voltage divider may form part of thezero-voltage switch.

Finally the preferred inventive regulator embodiment may also comprise atemperature regulator operatively connected with the housing or conduitin which a uniform temperature is to be maintained, for controlling theignition pulse circuit. The temperature regulator may include a Schmitttrigger and may have two-stage regulation.

Other objects and many of the attendant advantages of the invention willbe readily appreciated as the same becomes better understood byreference to the following detailed description, when considered withthe accompanying drawings, wherein FIG. 1 is a diagram illustrating theoperation of the analog-type constant-current regulator according to theinvention, wherein current values are plotted against the angles ofignition and of current flow, showing the basic load and the usefulcontrol range of the regulator;

FIG. 2 is a somewhat schematic block diagram illustrating the functionof the regulator according to the invention, with the more importantcircuit elements shown in block form and in their correlation;

FIG. 3 is a detailed circuit diagram showing the electrical componentparts of the regulator in a preferred, exemplary embodiment.

FIGS. 4a and 4b are explanatory diagrams of respective courses ofangular current-flow changes, at various firing times (180 and 45",respectively), for one full cycle of the alternating current. FIG. 4aillustrates the prior art.

The diagram of FIG. 1 shows the operation of the analog-type regulatoraccording to the invention, and illustrates its function. The object ofthe invention is to permit the load to change within limits greater than1:3. Therefore, the desired current value must be adjustable only withina range of between l3 and of the forward flow angle of the actualcurrent in the circuit, as can be seen in the diagram (delimitedessentially by the legend Control Range).

Within the control range, the desired-value curve may be illustratedwith a sufficient precision by three straight lines. This involves thatthe above-mentioned flow-angle function may be substituted by anotherfunction, consisting in the subtraction or addition of voltages.

Considering the circuitry to be provided, this is attained in such amanner that there is provided a desired-value voltage divider B (seeFIG. 2) whereto a positive voltage is applied, and that the divider iscorrected by a negative voltage increasing with a decreasing flow angle,and is affected by a supplemental load of a Zener diode and a resistor,forming part of the voltage-divider circuit. Besides, with regard to thevoltage, an actual-value rectifier D has a high value owing to negativefeedback resistors used in the circuitry. Due to a particular design ofthe above-said rectifier an accuracy greater than 99 percent may beachieved of the earlier discussed theoretical function.

The block diagram of FIG. 2 illustrates the function of the analog-typeregulator according to the invention when dealing with alternatingcurrent. A main circuit includes a load R (not identified as such inFIG. 3), a transducer m in actual-value rectifier D and a final controlelement preferably in the form of a Triac, designated T15. The currentis measured as a controlling parameter between the load and the Triac,and it is compared with the corrected desired value which latter derivesits influencing value from the voltage drop across the Triac.

The desired and actual current values are compared in a differentialamplifier including, as a matter of example, circuit sections E, H. Theyare provided with an RCR member for achieving the necessary regulatingaction. The output signal of this amplifier charges a capacitor, whichin turn discharges through a synchronizing stage I during each zero-axiscrossing of the network voltage. Whenever the charging voltage of thecapacitor exceeds a predetermined value, a Schmitt trigger K is trippedto reverse, and then charges a capacitor. As soon as the latter attainsa predetermined voltage value, an ignition pulse stage L is fired andthe capacitor discharges across the gate of Triac T which then becomesconductive.

FIG. 2 also shows a desired-value rectifier circuit A, associated withthe afore-mentioned voltage divider B, and serving to set the desiredvalue. The diagram also includes an optional two-step temperatureregulator M which will be explained as the description proceeds,together with certain prominent elements of the circuitry also shown inFIG. 2 but not referred to so far (such as diodes D9, D10, D15, D16;resistor R37). The schematic diagram also shows a 220 AC networkconnection including a phase line identified as R and a neutral linemarked M in addition, FIG. 3 shows a line X leading to the primary oftransducer m in the complete circuit of the preferred embodiment. Thehousing may be grounded, as usual (indicated in FIG. 3).

In the circuit diagram of the inventive analog-type regulator in itspreferred, exemplary embodiment, as shown in FIG. 3, the voltage droppedacross Triac T15 is led to desired-value rectifier A which includes adiode D1, resistors R1, R2, R3, R5, a capacitor C1 and a Zener diode D2.The latter is provided in the device for making the direct voltage oncapacitor C1 independent of the network voltage value so that the directcurrent is simply a function of the current flow angle. The directvoltage is negative with reference to the zero point of the circuit.

The appropriate desired-value voltage is generated by voltage divider Bincluding a resistor R4, a Zener diode D3 and the internal resistance ofthe justdescribed desired-value rectifier, and is available across diodeD3; this voltage is positive.

It will be shown in equations and diagrams that the direct currentobtained from the desired-value rectifier circuit A is a function of thecurrent flow angle through the Triac T15 which constitutes the finalcontrol element in the inventive regulator. The following mathematicaldefinitions and stipulations should be con-- sidered:

u U sm t 0= U- 2 (full sine wave) The voltage of the desired-valuerectifier can be derived, as will appear from the equations, where I.URJLS' Values 2. U values, and finally '3. Udemed values will bepresented, considering that U voltage of the desired-value rectifiercircuit U desired voltage of the same circuit when the current flowangle is 180 UMLS, effective voltage value at a particular current flowangle U arithmetic mean value of the voltage at a particular currentflow angle t= firing time or firing angle u instantaneous voltage Uamplitude voltage U= r.m.s. (effective) mean voltage value at a currentflow angle of 180 (full sine half-wave) J1" U-sin mu 17f: sin t-dtUAVERAGE desired R.M.8.

delircd= 180 delired denired 180 deuired various firing times (180 and45, respectively), each time for one full cycle of the alternatingcurrent.

By reason hereof any increase of the voltage on the desired-valuerectifier involves a decrease of the desired value.

In order to make the latter dependent on the flow angle, the voltagedivider is connected to and is charged by a resistor Zener diodecombination C, i.e. a circuit including resistors R6, R7 and a Zenerdiode D4. There are provided capacitors C2, C3 for suppressinghighfrequency oscillations.

Actual-value rectifier D provides a direct voltage at resistors R23, R24(the latter being preferably variable), the voltage correspoding to thearithmetical average value of the current. The rectifier includes atransducer (preferably in the form of a transformer) m, a basic loadR26, diodes D9, D10, resistors R25, R27, R28, the afore-mentionedresistors R23, R24 and a capacitor C6.

Resistor R24 is in the form of a trimmer. On this resistor it ispossible to set the magnitude of the desired effective constant current.From the standpoint of the potential, actual-value rectifier D iscoupled positively against the zero point across a voltage divider Fwhich includes resistors R8, R20, R21, as well as across a Zener diodeD5. Consequently the component tolerances of the earlier-discusseddesired-value rectifier A can be compensated by changes in resistorsR20, R21.

On the other hand, negative feedback on differentialamplifier circuit Eis achieved across voltage divider F, formed by resistors R20, R21 andanother resistor R22, a capacitor C7 and Zener diode D5.

Two input transistors T1, T2 of differential amplifier E are fed by aconstant-current source with a current resulting from the voltage dropon diode D5, a transistor T3 and a resistor R12. The input transistorsas well asresistors R10, R11 form a bridge which is balanced only if thesame voltage flows through both transistors T1, T2. This conditions adifferential voltage of zero volts while any individual voltage at theinput of differential amplifier E must be greater than the voltage ondiode D5.

The detuning of the bridge is one-sidedly evaluated by transistors T4,T5. Through a resistor R9 associated with transistor T4, there alsoflows the constant current while the emitter voltage of transistors T4,T is kept.

high by a Zener diode D7. The amplifier is therefore blocked when thereis a negative detuning voltage. A resistor R13 supplies Zener diode D7with a minimum current which provides a sufficient steady voltage forsaid diode.

A diode D6 provides protection against high negative voltages. Aresistor R14 of transistor T5 has available a voltage proportional tothe positive differential voltage. This voltage is supplied to anend-stage transistor T6, in block G, of a grounded-collector circuitacross an RCR member including resistors R15, R16, R17 and a capacitorC4. The RCR member provides the necessary regulating effect which isapproximately proportional integral.

Another differential-amplifier circuit H, at the emitter of transistorT6, supplies its output signal to the negative feedback, on the onehand, and to a capacitor C5 via a resistor R18 and a Zener diode D8, onthe other hand. A resistor R19 restricts the discharge current.

The discharge of capacitor C5 is carried out by a synchronizingzero-voltage (passage) switch 1 during each zero crossing in the networkvoltage unless said switch is blocked. The zero-voltage switch, being asynchronizing stage of the device, includes a phase-correcting voltagedivider provided with resistors R45, R46, a capacitor C11 and theinternal resistance in the switching circuit. A capacitor C12 isprovided for suppressing coupling oscillations. An output transistor Tof the switch discharges capacitor C5 across resistor R19 when it hasbeen energized.

Transistor T10 is energized only when a transistor T9 is not energizedor when no sufficiently negative voltage is available through acooperating diode D16. This occurs during the negative half-wave of thenetwork voltage. The positive half-wave controls transistor T9 across adiode D15. Therefore the current controlling transistor T10 can flowthrough a resistor R44 only during the zero crossing of the networkvoltage. Any voltage present on a resistor R42 blockssynchronizingzero-voltage switch I, and capacitor C5 is not dischargedany more. Resistors R43, R47 form a symmetrical base load for thejust-described voltage divider.

The charging voltage of capacitor C5 is controlled by Schmitt trigger K.This includes resistors R48, R49, R50, R51, R52, R53, as well astransistors T11, T12. Whenever the voltage on capacitor C5 reaches aparticular value, the Schmitt trigger is switched. its output voltage,present on resistor R53, charges a capacitor C13 across a diode D17.

Transistors T13, T14 and resistors R54, R55, R56 perform the function ofignition device L. Capacitor C13 is discharged across this arrangementinto a current-limiting resistor R57 and through the gate of theearlier-mentioned Triac T15 so that the latter ignites.

When this happens, the regulator M, acting as a blocking circuit, isactivated which is an electronic twostep temperature regulator providedwith a second Schmitt trigger which latter includes resistors R38, R39,R40 and coacting with the earlier-mentioned resistor R53, a diode D14and transistors T7, T8. In this circuit, resistor R53 also functions asthe working resistor of the Schmitt trigger for the ignition circuit, iefor diode D14 and transistors T7 T8.

P Within the scope of obtaining a low switching hysteresis, the secondSchmitt trigger includes said diode D14 as a resistance common to theemitters of transistors T7, T8. The input of the Schmitt trigger isconnected directly to a voltage divider including a trimmer R35, aresistor R36 and a thermistor R37. The dividing ratio is influenced by aheat conductor constituted by thermistor R37. The switching pointcorresponding to the desired temperature is set at trimmer R35.

If there is a drop below a certain predetermined temperature, theSchmitt trigger of circuit M turns on the regulator so that theoperating range circuit of the regulator has coupled thereto the Schmitttrigger in which case transistor T7 conducts whilst transistor T8 is cutoff.

In this event the voltage on resistor R38 of transistor T8 is coupled tothe input of blocking and synchronizing switch M. If the two-steptemperature regulator is cut off, the synchronizing zero-passage switchis blocked and transistor T11 is actuated. Being so, ignition pulsestage L would have available the full voltage if transistor T8 were notactuated. In this way, the voltage is short-circuited. When thetemperature regulator operates, transistor T8 opens and the voltage onresistor R42 breaks down. Consequently the inventive analog-typeregulator is not influenced any more by the temperature regulator.

A power unit N of the device, fed by the 220 V AC line, is arranged towork on 24 volts or 12 volts. It includes resistors R29, R30, R31, R32,R33, R34, a diode D1], Zener diodes D12, D13 and capacitors C8, C9, C10.The operation of this unit will be readily understood by those skilledin the art and need not be explained in more detail.

An RC member 0, including a resistor R58 and a capacitor C14, isprovided to serve as a protective circuit for Triac T15 to prevent anyexcess voltage pulses reaching the same.

It should be understood, of course, that the foregoing disclosurerelates only to a preferred, exemplary embodiment of the invention, andthat it is intended to 1. An analog-type constant-current regulator forobtaining a desired value of a constant, effective alternating current,independent of its load, such as for providing a source of current formaintaining a uniform temperature by electric heating, e.g. inprotective housings and small-diameter conduits for the measurement offluid parameters; the regulator comprising, in combination: anactual-value rectifier circuit upon which the actual current value isimpressed; a controller circuit for adjusting the desired alternatingcurrent; a circuit for coupling said corrective value to a circuit forsetting said desired value; an average-value rectifier circuit formeasuring the load current; a differential amplifier circuit upon whichare impressed, and wherein are compared, the output of saidaverage-value rectifier circuit and the correcteddesired value for saidsetting circuit; a circuit for coupling the forward flow angle of saidactual current to an input circuit of said differential amplifier, as acorrective value for eliminating disturbance variables; a synchronizingcircuit; an ignition pulse cir-- cuit; said differential amplifiercircuit being connected, by the intermediary of said synchronizingcircuit and said ignition pulse circuit, to drive a control electrode insaid controller circuit; and a temperature regulator circuit,operatively connected with the housing or conduit in which said uniformtemperature is to be maintained, for controlling said ignition pulsecircuit, wherein said temperature regulator circuit includes two stagesfor incremental regulation.

2. The regulator as defined in claim 2, further comprising a phase-anglesplit control circuit capable of correcting variations of said load atleast within the ratio of 1:3.

3. The regulator as defined in claim 1, wherein said controller circuitis in the form of a Triac, said corrective value being derived from thevoltage drop across said Triac.

4. The regulator as defined in claim 3, further comprising a maincircuit including a series connection of said load with a transducerforming part of said actualvalue rectifier circuit and said Triac.

5. The regulator as defined in claim 3, further com prising a protectivecircuit for said Triac, in the form of at least one RC member, toprevent excess voltage pulses from reaching said Triac.

6. The regulator as defined in claim 1, further comprising elements insaid circuit for setting said desired value at least within the range of1 3 to 150 of said forward flow angle of the actual current.

7. The regulator as defined in claim 1, wherein said circuit for settingthe desired value is in the form of a desired-valuevoltage dividercircuit upon which is impressed a positive voltage, corrected by anegative voltage which increases with a decreasing value of said forwardflow angle of the actual current, and including a on said voltagedivider circuit, and at least one capacitor for suppressinghigh-frequency oscillations.

10. The regulator as defined in claim 1, wherein said differentialamplifier circuit includes two transistors connected to respectiveoutputs of said actual-value rectifier circuit and said circuit forsetting the desired value, said transistors forming part of a bridgecircuit which is balanced in the event of equal impressed voltagevalues.

11. The regulator as defined in claim 1, wherein said differentialamplifier circuit includes a capacitor which is charged by the output ofthe former and is in turn discharged through said synchronizing circuitduring each zero-axis crossing of the network voltage.

12. The regulator as defined in claim 1, wherein said differentialamplifier circuit includes circuit elements constituting a negativefeedback circuit.

13. The regulator as defined in claim 1, further comprising an end stageassociated with said differential amplifier circuit and including RCmembers providing an approximately proportional integral regulatingeffect.

14. The regulator as defined in claim 1, wherein said synchronizingcircuit is in the form of a zero-voltage switch associated with saidcontroller circuit.

15. The regulator as defined in claim 14, wherein said zerovoltageswitch includes a phase-correcting voltage divider circuit.

16. A constant-current regulator for obtaining a desired value of aconstant, effective alternating current, independent of the load and themains voltage, such as for providing a source of current for maintaininga uniform temperature by electric heating, e.g. in protective housingsand small-diameter conduits for the measurement of fluid parameters; theregulator comprising, in combination, a first circuit for making thedesired value dependent upon the phase angle of the current flow fromthe source of current, a differential amplifier circuit for comparingparameters of the load current and of a presettable corrected desiredvalue, and a second circuit for impressing a direct voltage upon theinput of said differential amplifier, wherein said direct voltage isdependent on the angle of current flow and constitutes the correctivevalue for disturbance variables.

17. The regulator as defined in claim 16, further comprising aphase-angle split control circuit for correcting variations of said loadat least within the ratio of 1:3.

18. The regulator as defined in claim 16, further comprising acontroller circuit in the form of a Triac, said angle of current flowbeing derived from the voltage drop across said Triac.

19. The regulator as defined in claim 18, further comprising a maincircuit including a series connection of said load with a transducer,forming part of an actual-value rectifier circuit upon which the actualcurrent value is impressed, and said Triac.

20. The regulator as defined in claim 18, further comprising aprotective circuit for said Triac, in the form of at least one RCmember, to prevent excess voltage pulses from reaching said Triac.

211. The regulator as defined in claim 16, further comprising a thirdcircuit for coupling said direct voltage to a fourth circuit forachieving said desired value.

22. The regulator as defined in claim 21, wherein said fourth circuit isin the form of a voltage divider circuit upon which is impressed apositive voltage, corrected by a negative voltage which increases with adecreasing value of said angle of current flow, and including asupplemental load circuit.

23. The regulator as defined in claim 22, wherein said supplemental loadcircuit includes a Zener diode and at least one resistor.

24. The regulator as defined in claim 23, further comprising a fifthcircuit including a Zener diode and at least one resistor for makingsaid desired value dependent on said voltage divider circuit.

25. The regulator as defined in claim 16, further comprising a rectifiercircuit for measuring the load current, thus acting as an average-valuerectifier, a synchronizing circuit, and an ignition pulsecircuit,whereby said differential amplifier circuit is connected to a controlelectrode in said controller circuit by way of said synchronizingcircuit and said ignition pulse circuit.

26. The regulator as defined in claim 25, further comprising atemperature regulator circuit, operatively connected with the housing orconduit in which said uniform temperature is to be maintained, forcontrolling said ignition pulse circuit, said temperature regulatorcircuit having two stages for incremental regulation.

27. The regulator as defined in claim 16, further comprising elementsfor setting said desired value at least within the range of 13 to 150 ofthe forward flow angle of the actual current.

28. The regulator as defined in claim 16, wherein said differentialamplifier circuit includes two transistors forming part of a bridgecircuit which is balanced in the event of equal impressed voltagevalues, one of said transistors being connected to the output of saidsecond circuit while the other transistor is connected to the output ofan actual-value rectifier circuit upon which the actual current value isimpressed.

29. The regulator as defined in claim 16, wherein said differentialamplifier circuit includes a capacitor which is charged by the output ofthe former and is in turn discharged during each zero-axis crossing ofthe mains voltage.

30. The regulator as defined in claim 16, wherein said differentialamplifier circuit includes circuit elements constituting a negativefeedback circuit.

31. The regulator as defined in claim 16, further comprising an endstage associated with said differential amplifier circuit and includingRC members providing an approximately proportional integral regulatingeffect.

32. The regulator as defined in claim 16, further comprising asynchronizing circuit in the form of a zero-voltage switch operativelyassociated with said differential amplifier circuit.

33. The regulator as defined in claim 32, wherein said zero-voltageswitch includes a phase-correcting voltage divider circuit, and furthercomprising a controller circuit in the form of a Triac, said correctivevalue being derived from the voltage drop across said Triac, saiddifferential amplifier circuit being connected, by the intermediary ofsaid synchronizing circuit, to drive a control electrode in said Triac.

1. An analog-type constant-current regulator for obtaining a desiredvalue of a constant, effective alternating current, independent of itsload, such as for providing a source of current for maintaining auniform temperature by electric heating, e.g. in protective housings andsmall-diameter conduits for the measurement of fluid parameters; theregulator comprising, in combination: an actual-value rectifier circuitupon which the actual current value is impressed; a controller circuitfor adjusting the desired alternating current; a circuit for couplingsaid corrective value to a circuit for setting said desired value; anaverage-value rectifier circuit for measuring the load current; adifferential amplifier circuit upon which are impressed, and wherein arecompared, the output of said average-value rectifier circuit and thecorrected desired value for said setting circuit; a circuit for couplingthe forward flow angle of said actual current to an input circuit ofsaid differential amplifier, as a corrective value for eliminatingdisturbance variables; a synchronizing circuit; an ignition pulsecircuit; said differential amplifier circuit being connected, by theintermediary of said synchronizing circuit and said ignition pulsecircuit, to drive a control electrode in said controller circuit; and atemperature regulator circuit, operatively connected with the housing orconduit in which said uniform temperature is to be maintained, forcontrolling said ignition pulse circuit, wherein said temperatureregulator circuit includes two stages for incremental regulation.
 1. Ananalog-type constant-current regulator for obtaining a desired value ofa constant, effective alternating current, independent of its load, suchas for providing a source of current for maintaining a uniformtemperature by electric heating, e.g. in protective housings andsmall-diameter conduits for the measurement of fluid parameters; theregulator comprising, in combination: an actual-value rectifier circuitupon which the actual current value is impressed; a controller circuitfor adjusting the desired alternating current; a circuit for couplingsaid corrective value to a circuit for setting said desired value; anaverage-value rectifier circuit for measuring the load current; adifferential amplifier circuit upon which are impressed, and wherein arecompared, the output of said averagevalue rectifier circuit and thecorrected desired value for said setting circuit; a circuit for couplingthe forward flow angle of said actual current to an input circuit ofsaid differential amplifier, as a corrective value for eliminatingdisturbance variables; a synchronizing circuit; an ignition pulsecircuit; said differential amplifier circuit being connected, by theintermediary of said synchronizing circuit and said ignition pulsecircuit, to drive a control electrode in said controller circuit; and atemperature regulator circuit, operatively connected with the housing orconduit in which said uniform temperature is to be maintained, forcontrolling said ignition pulse circuit, wherein said temperatureregulator circuit includes two stages for incremental regulation.
 2. Theregulator as defiNed in claim 2, further comprising a phase-angle splitcontrol circuit capable of correcting variations of said load at leastwithin the ratio of 1:3.
 3. The regulator as defined in claim 1, whereinsaid controller circuit is in the form of a Triac, said corrective valuebeing derived from the voltage drop across said Triac.
 4. The regulatoras defined in claim 3, further comprising a main circuit including aseries connection of said load with a transducer forming part of saidactual-value rectifier circuit and said Triac.
 5. The regulator asdefined in claim 3, further comprising a protective circuit for saidTriac, in the form of at least one RC member, to prevent excess voltagepulses from reaching said Triac.
 6. The regulator as defined in claim 1,further comprising elements in said circuit for setting said desiredvalue at least within the range of 13* to 150* of said forward flowangle of the actual current.
 7. The regulator as defined in claim 1,wherein said circuit for setting the desired value is in the form of adesired-value voltage divider circuit upon which is impressed a positivevoltage, corrected by a negative voltage which increases with adecreasing value of said forward flow angle of the actual current, andincluding a supplemental load circuit.
 8. The regulator as defined inclaim 7, wherein said supplemental load circuit includes a Zener diodeand at least one resistor.
 9. The regulator as defined in claim 8,further comprising a circuit including a Zener diode and at least oneresistor for making said desired value dependent on said voltage dividercircuit, and at least one capacitor for suppressing high-frequencyoscillations.
 10. The regulator as defined in claim 1, wherein saiddifferential amplifier circuit includes two transistors connected torespective outputs of said actual-value rectifier circuit and saidcircuit for setting the desired value, said transistors forming part ofa bridge circuit which is balanced in the event of equal impressedvoltage values.
 11. The regulator as defined in claim 1, wherein saiddifferential amplifier circuit includes a capacitor which is charged bythe output of the former and is in turn discharged through saidsynchronizing circuit during each zero-axis crossing of the networkvoltage.
 12. The regulator as defined in claim 1, wherein saiddifferential amplifier circuit includes circuit elements constituting anegative feedback circuit.
 13. The regulator as defined in claim 1,further comprising an end stage associated with said differentialamplifier circuit and including RC members providing an approximatelyproportional -integral regulating effect.
 14. The regulator as definedin claim 1, wherein said synchronizing circuit is in the form of azero-voltage switch associated with said controller circuit.
 15. Theregulator as defined in claim 14, wherein said zero-voltage switchincludes a phase-correcting voltage divider circuit.
 16. Aconstant-current regulator for obtaining a desired value of a constant,effective alternating current, independent of the load and the mainsvoltage, such as for providing a source of current for maintaining auniform temperature by electric heating, e.g. in protective housings andsmall-diameter conduits for the measurement of fluid parameters; theregulator comprising, in combination, a first circuit for making thedesired value dependent upon the phase angle of the current flow fromthe source of current, a differential amplifier circuit for comparingparameters of the load current and of a presettable corrected desiredvalue, and a second circuit for impressing a direct voltage upon theinput of said differential amplifier, wherein said direct voltage isdependent on the angle of current flow and constitutes the correctivevalue for disturbance variables.
 17. The regulator as defined in claim16, further comprising a phase-angle split control circuit forcorrecting variations of said lOad at least within the ratio of 1:3. 18.The regulator as defined in claim 16, further comprising a controllercircuit in the form of a Triac, said angle of current flow being derivedfrom the voltage drop across said Triac.
 19. The regulator as defined inclaim 18, further comprising a main circuit including a seriesconnection of said load with a transducer, forming part of anactual-value rectifier circuit upon which the actual current value isimpressed, and said Triac.
 20. The regulator as defined in claim 18,further comprising a protective circuit for said Triac, in the form ofat least one RC member, to prevent excess voltage pulses from reachingsaid Triac.
 21. The regulator as defined in claim 16, further comprisinga third circuit for coupling said direct voltage to a fourth circuit forachieving said desired value.
 22. The regulator as defined in claim 21,wherein said fourth circuit is in the form of a voltage divider circuitupon which is impressed a positive voltage, corrected by a negativevoltage which increases with a decreasing value of said angle of currentflow, and including a supplemental load circuit.
 23. The regulator asdefined in claim 22, wherein said supplemental load circuit includes aZener diode and at least one resistor.
 24. The regulator as defined inclaim 23, further comprising a fifth circuit including a Zener diode andat least one resistor for making said desired value dependent on saidvoltage divider circuit.
 25. The regulator as defined in claim 16,further comprising a rectifier circuit for measuring the load current,thus acting as an average-value rectifier, a synchronizing circuit, andan ignition pulse circuit, whereby said differential amplifier circuitis connected to a control electrode in said controller circuit by way ofsaid synchronizing circuit and said ignition pulse circuit.
 26. Theregulator as defined in claim 25, further comprising a temperatureregulator circuit, operatively connected with the housing or conduit inwhich said uniform temperature is to be maintained, for controlling saidignition pulse circuit, said temperature regulator circuit having twostages for incremental regulation.
 27. The regulator as defined in claim16, further comprising elements for setting said desired value at leastwithin the range of 13* to 150* of the forward flow angle of the actualcurrent.
 28. The regulator as defined in claim 16, wherein saiddifferential amplifier circuit includes two transistors forming part ofa bridge circuit which is balanced in the event of equal impressedvoltage values, one of said transistors being connected to the output ofsaid second circuit while the other transistor is connected to theoutput of an actual-value rectifier circuit upon which the actualcurrent value is impressed.
 29. The regulator as defined in claim 16,wherein said differential amplifier circuit includes a capacitor whichis charged by the output of the former and is in turn discharged duringeach zero-axis crossing of the mains voltage.
 30. The regulator asdefined in claim 16, wherein said differential amplifier circuitincludes circuit elements constituting a negative feedback circuit. 31.The regulator as defined in claim 16, further comprising an end stageassociated with said differential amplifier circuit and including RCmembers providing an approximately proportional -integral regulatingeffect.
 32. The regulator as defined in claim 16, further comprising asynchronizing circuit in the form of a zero-voltage switch operativelyassociated with said differential amplifier circuit.